20 degrees advance? Check your service manual... that's a lot. 25 is way too
much.
You are aware that you are supposed to disconnect the vacuum advance line
and block it off when checking timing?
Also, there is no need to mess with the carbs due to timing adjustments --
they are completely independent systems.
It sounds to me that (1) you are measuring timing incorrectly, for whatever
reason (and several possibilities spring to mind); and (2) your drivability
problems are due to the carburetor adjustments (although, since you violated
the rule of experimentation and did two things at the same time, it is
difficult to determine -- it might well mean retarded timing).
Ways in which you may have misinterpreted the timing :
1. checking it with the vacuum advance operative (thus advancing it,
relative to engine RPM)
2. checking at too high an idle speed (so that mechanical advance is taking
effect, also resulting in a high reading)
3. misinterpreting the timing marks as meaning 10 degree intervals instead
of 5 degrees, or whatever (different models have different marks)
4. TDC is incorrectly marked on the balancer (due to incorrect balancer
being used by DPO, or slippage of outer ring due to delamination of rubber
isolator)
First I would attempt to determine why the timing was not in the 5-15 degree
advanced range, which would be more reasonable. Resolving that, if matters
had not improved, I would start over on the carbs, assuming I had made a
mistake somewhere.
Hope this helps.
on 6/26/03 7:24 PM, MonteMorris at mmorris@nemr.net wrote:
> I know, I know; "If it ain't broke, don't fix it", but I did anyway:-(.
> The car has been running real well (650 miles RT to St. Louis last weekend),
> but for the last several weeks I've been trying to "tweek" the timing on the
> 67B with points dizzy using the A-R adjustment knob. I knew it was somewhat
> off, even though it was running well. I used the timing light and it showed
> about 25 degrees advanced, so I backed it off to 20 degrees. I figured I'd
> better readjust the carbs to the new timing, so I did this, put in a new
> choke cable and set it back up, and checked the plugs and regapped them.
> Now the car is running like sh*t! It's backfiring upon deceleration and
> missing upon acceleration.
> What should I check first?
> Monte
>
--
Max Heim
'66 MGB GHN3L76149
If you're near Mountain View, CA,
it's the primer red one with chrome wires
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